Oh my, he is really munching away!
My best suggestions would be: more plants, especially floating/upper level ones; and trying Indian Almond Leaf.
Also, does this tank have a cover? If not, I'd be worried about him jumping out.
Personally, I don't know anything about real plants, but there are people on here who do. Some more tall, soft, fake ones that reach the surface help provide shady hidey-holes for now, and help him feel less exposed to predators.
Indian almond leaf isn't grown in the tank, but they are sometimes placed in the tank. Some fish find the tannins soothing.
Almost anything would work for a temporary cover... plastic wrap with little holes... maybe plastic canvas cut to fit.